Catalytic conversion of oils



Feb. 25, 1947.

.1. M. BRACKENBURY CATALYTIC CONVERSION OF OILS Filed July 31. 1944 2Sheets-Sheet l' k cnbur l omwmm uc=omsw cE20u rwznfo r: John M. brac Dghi5 AHornzg:

cE2ou wciao Feb. 25, 1947.

J. M. BRACK ENBURY CATALYTIC CONVERSION OF OILS 2 Sheets-Sheet 2 FiledJuly 31, 1944 lnvenior I John M Brackznbur Bg hi5 Aflornag! bestobtainable quality.

portant of the available tools-at the refiners- Patented Feb. 25, 1947UNITED STATE CATALYTIC CONVERSION OF OILS,

John M. Brackenbury, Oakland, Calif., assignor' to Shell DevelopmentCompany, San Francisco, Callf., a corporation of Delaware ApplicationJuly 31', 1944, Serial No. 547,445

This invention relates to. the catalytic conversion of hydrocarbon oilswith finely divided catalysts in fluid catalyst systems wherein thefinely divided catalyst is continuously recycled through a conversionzone'and through a separate regeneration zone. A particular aspect ofthe inven-' tion relates to the catalytic cracking of varioushydrocarbon oils to produce valuable normally gaseous and normallyliquid hydrocarbon products of lower molecular weight. A preferredmodification of the invention relates to a combination process for thetreatment of petroleum by the means of which superior Diesel fuels andfuel oils may be produced without sacrifice in the production of qualitygasoline.

The nature of the invention may be most conveniently set forth by firstdescribing a specifi preferred modification thereof.

When petroleum oil is received at the refinery the gases and so-calledstraight run gasoline are removed leaving a. partly reduced crude. Therefiner is then faced with the problem of pro- .6 Claims (Cl. 196-'-50).2 I I V secondary products or treated by thermal methods, although inafew cases they are catalytically cracked along with the light gas oil.Also, the bottom fraction, or reduced crude cannot be com pletelyvaporized and is not suited for vapor phase catalytic cracking. Inpractice the gas oil and .stoveoil are removed as completely as possibleunder ordinary fractionation conditions to leave a reduced'crude whichis suitable for use as fuel ducing the maximum quantity ofqualityproducts from this partly reduced crude. One of the considerableeffort and attention has therefore been given to various ways and meansfor producing the maximum uantity of gasoline of the One of the mostimdisposal is catalytic cracking. Due to the large demand for gasoline,catalytic cracking is becoming almost universally used. Even with the 1best means available, however, it is not practical to convert all ofthis partly reduced crude to gasoline and there is left therefore aconsiderable volume of by-product materials of Jesser value. In the pastthe emphasis has been largely on the production of the maximumquantities of gasoline of the best quality and the byproducts formed orleft have largely determined A eral the feeds preferred and used forcatalytic cracking units are those fractions taken from the middle ofthe partly reduced crude. These fractions are of the nature of light gasoil or stove oil. The lower boiling components of the nature of heavygasoline, naphtha and kerosene are more refractory and are generallyused in oil- Ina few cases this reduced crude has been partl'yivaporizedin 'a so-called contact vaporizer andthe vapors cracked along with'thegas oils:

of quality gasoline are generally produced,'but

only at the expense of the quantity and quality of various otherpetroleum products such as Diesel oil and fuel oil. A primary object ofthe particular modification of the invention about to be described is toprovide a. method whereby the petroleum may be utilized to'betteradvantage by producing quality gasoline from the more refractoryfractions of the partly reduced crude without sacrificing yield orquality of secondary products.

To the accomplishment of this and related objects the partly reducedcrude is separated by fractional distillation into a naphtha (or heavygasoline) fraction, a heavy reflux condensate including kerosene, gasoil and stove oil, and a reduced crude. The reduced crude is not howeverthermally cracked as is the general practice, but is subjected to afiash distillation under reduced pressure to produce a heavy flashedcondensate and a heavy tar residue. The naphtha fraction and the heavyflashed condensate are then simultaneously cracked catalytically. Thenaphtha and the heavy fiashed'condensate are both relatively refractorymaterials and are individually less suited for catalytic cracking thanthe intermediate gas oil and stove .oil fractions. It has been found,however, that these two refractory stocks may advantageously becatalytically cracked together under suitable conditions. By producingthe major part of the cracked gasoline from these materials excellentyields of quality gasoline may be produced without sacrifice of takenor: via line l2.

quality Diesel fuel production and while afl'ording a superior fuel oil.However, because of the totally dif erent characters of these two feedstocks and the greater refractivity of the naphtha fractions the maximumeflicient production of gasoline is not obtained when cracking thesemixed feeds simultaneously under the usual cracking conditions. Thecracking of these two stocks simultaneously under optimum conditions iseffected, according to the process of the present invention, ashereinafter described.

The process will be described in the following in connection withFigures I and II of the accompanying drawing in which this specificembodiment of the invention is set forth for purposes of illustration.In the accompanying drawing, Figure I is a simplified flow diagramwherein there is shown by means of diagrammatic figures, not drawn toscale, one suitable assembly of apparatus arranged for operationaccording to this particular embodiment of the invention. ure II is adiagrammatic illustration of a suitable reactor in section.

The charging stock is a crude petroleum or one from which the gasolinehas been substantially removed. If a crude petroleum containing gasolineis used, the gasoline is preferably removed to leave a partly reducedcrude havin an initial boiling point of at least 300 F. The feed is thenseparated by distillation into a naphtha fraction, 9. heavy refluxcondensate and a reduced crude. The cut point between the naphtha andthe reflux condensate may vary considerably, but is preferably betweenabout 400 F. and 500 F.

.is charged by pump 2 to a stripping column 3 wherein gasoline andnaphtha ar separated. The gasoline and naphtha are removed overhead Inthe modifil via line 4. Part of the condensate is returned as phericpressure without substantial cracking are removed. Thqvarious productsmay be removed in a single stream or may be segregated into variousfractions as desired. Thus, for example, in the arrangement shown, aheavy naphtha or kerosene fraction is removed via line H); a light gasoil fraction suitable for use as Dieselfuel is taken 01! via line I I;and a heavy gas oil fraction suitable for use as Diesel fuel or forstove oil is The bottom product is a reduced crude suitable for use asfuel oil.

The reduced crude is passed through heating coils in a suitable heaterand then via line l3 and pressure .control valve l3a to a vacuum flashcolumn M wherein it is vacuum flashed under conditions chosen to removeoverhead from between about 40% and about 75% of a heavy flashedcondensate having a molecular weight between about 2'70 and about 350.One set of typical conditions is, for example, a temperature of about700 to 750 F. and 100 mm. absolute pressure. Steam may be injected vialine It to aid in decreasing the residence time and prevent cracking.The flashing operation does not involve any appreciable amount ofcracking. This is indicated by the average molecular weight of theflashed condensate. Thus, the average molecular weight of the flashedcondensate when taking 45% overhead is about 280, and the averagemolecular weight when taking overhead is about 345. In general acondensate having an average molecular weight in this range isindicated. This flashed condensate, it is seen, represents the heaviestportion of the petroleum that can be vaporized with available equipmentwithout substantial cracking. It is diflicult to vaporize, andinvariably contains appreciable amounts of nitrogen compounds and otherimpurities.

The material removed from the bottom of the flash column I4 is a heavyviscous residue. This material is totally unsuited for fuel oil, butproduces a superior fuel oil when combined with aromatic refluxcondensate as hereinafter described.

In a preferred modification of the process of the invention the flashingoperation is carried out under somewhat more severe conditions to effecta slight controlled amount of cracking. The

amount of. cracking is adjusted to give between about 50% and of acondensate having an average molecular weight between about 280 and 300.This may be and is preferably efiected with the formation of not morethan 1% gas and not more than 1% of gasoline, i. e., normally liquidproducts boiling up to 405 F. This operation is effected at temperaturesbelow about 840 F., for instance temperatures between about 780 F. and800 F. The conditions of pressure and residence time to give this resultcannot be stated with any degree ,of deflniteness due to theinterrelation of these factors and the differences due to the particularpetroleum source and apparatus effects. However, these conditions areadjusted in the known manner and may be readily arrived at in anyparticular case. The distillate obtained under such conditions ishereinafter referred to as flash cracked'condensate.

The naphtha fraction separated in column 5 is fed by line I to asuitable fluidized catalyst cracking reactor IT. This feed picks up andcarries to the reactor a quantity of hot freshly regenerated catalystfrom the standpipes l8 and IQ of the fluidized catalyst regenerator 20.In some cases the heat supplied by the hot freshly regenerated catalystmay be sufliclent to vaporize the naphtha and heat it to the .desiredcracking temperature. The naphtha is however quite refractory and forbest results is cracked at temperatures higher than those generallyapplied for the catalytic cracking of gas oils and similar stocks.

It is therefore generally necessary to preheat the naphtha feed prior tocontacting it with the catalyst. ,Thus, the naphtha feed may .be passedthrough the coils of a suitable heater 2|- The naphtha containingsuspended freshly regenerated catalyst is introduced into the fluidizedcatalyst reactor at or near the bottom in the conven- The preheated upand carried to the regenerator 20 by a stream] of regenerationgasentering via 'line 26. Spent V regeneration gas is withdrawn from thesystem by line- 21.

cracked products is passed, as a vapor substan-3 The mixture of crackedand ungasoline may be returned to the-column 29 for reflux. Theremainder is withdrawn via line 33.

A heavy highly aromatic condensate'is removed via line 35, cooler 36,surge tank 31 and pump 38 and a heavy residue is removed vialine 34'.This heavy residue contains a small amount of catalyst and may beadvantageously recycled back to the cracking reactor via-line 1. Thecondensate consists largely of highly refractory aromatic hydrocarbonsproduced in the cracking zone. This material is passed via line 39 to atank 4| wherein it is blended with the hot vacuum flashed residue,coming from the vacuum flash column 14 via line 42. In view of thehighly aromatic nature of the condensate it blends well with the veryvheavy.

vacuum flashed residue toproduce a stable and superior fuel'oil. Alsodue to its extreme .refrac small volume of material is capable ofconverting a relatively large volume of heavy vacuum flashed it requiresonly about 50 parts of the aromatic condensate to convert 100 parts ofthe heavy flashed residue into a superior 100 second (Say-'bolt-Furol-122 F.) fuel oil. When blended 1:1 the heavy flashed residueis converted to a-stable- 25 second (Saybolt-Furol-122 F.) fueloilmeeting the Navy special grade specifications.

Figure II is a somewhat more detailed illustration of the fluid catalystreactor IT. The naphtha and finely divided catalyst are introduced atthe bottom via line 'I and the distributing manifold 45. Partially spentcatalyst is withdrawn from the bottom via standpipes 24 and 25. Therates of addition and withdrawal of catalyst are so adjusted as tomaintain in the reactor a substantial bed of the catalyst asillustrated. The rate of flow of vapors is so controlled that thecatalyst is maintained in a pseudo liquid or fluidized state. Theflashed condensate or flash cracked condensate entering via line 23 isinjected into the fluidized bed of catalyst by means of a distributingmanifold 46. The reactor at the height of the manifold 46 is preferablyincreased in diameter, as shown, so as to accommodate the increasedvolume of vapors contacting the upper half of the fluidized bed ofcatalyst. The space in the reactor above the catalyst bed is provided toallow separation of, suspended particles of the catalyst from the vaporsleaving the catalyst bed.

A number of cyclone separators 4'! may advan- 65 tageously be providedin the upper disengaging space to afford a more complete removal ofsuspended catalyst pa'rticles. I l

The described embodiment of the invention .may be carried out using anyof the solid refractory metal oxide or clay-type cracking catalysts.

Suitable catalysts are, ,for example, the synthetic 6 I mina-boricoxide, silica-alumina-boric oxide and silica gel promoted with one ormore metal oxides adsorbed thereon. Also the natural or treated .1 claycatalysts such as material known as Filtrol comprise minor amounts ofpromoting compounds such as the oxides or sulfides of molybdenum,chromium, tungsten, vanadium and the like. These various crackingcatalystsare not necessarily equivalent and by the proper choice ofcatalyst it is possible to obtain almost any desired balance of suchfactors asthe concentration of butylenes in the gaseous products, etc. A

balance of products particularly suitable for pres.. 1 5 entrefineryoperation is obtained with the following proprietary cracking catalysts;boric oxide on peptized alumina, silica-alumina composite crackingcatalysts, and. silica-magnesia composite cracking catalysts. r

As pointed out above the feed stocks cracked according to the describedmodification of the invention are relatively refractory, i. e., undernormal cracking conditions such as used for cracking a clean naphthenicgas oil, the productivity of the two feeds are however different innature. The nephtha feed is inherently refractory due to the relativelylow molecular weight of the hydrocarbon constituents- The flashedcondensate and flash cracked condensate on the other hand are composedof hydrocarbons of high molecular weight and the refractivity appears tobe largely due to the presence of minor amounts of poisons such asnitrogen bases, etc.,

therefore actually less refractory than the naphtha and is preferablycracked under different conditions. According to the process of theinvention such less refractory materials are cracked under the optimumtemperature conditions for the combined feeds but at a higher spacevelocity. This is accomplished by supplying all or the major part of thehot, fresh catalyst with the more refractory naphtha and introducing.the 5 flashed condensate or flash cracked condensate at an intermediatepoint in the reaction zone as described. By control of the ratesof oilflow and/or by control of the depth of the bed of fluidized catalystmaintained in the reaction zone a soconslderable variation of the spacevelocities for the individual feeds may be obtained. Thus, the naphthafraction may be cracked at a weight hourly space velocity of, forexample, 0.4 to 2 pounds of oil per pound of catalyst per hour and theflashed condensate or flashv cracked condensate may be simultaneouslycracked at a higher,

pounds of upon the characters of the individual feed stocks,

the space velocities employed, etc. These are adjusted in the knownmanner to afiord the desired results for the particular operation athand. The approximate ranges of the individual conditions for generaloperation are as follows:

Temperature F 825-1100 Pressure .'...p. s. i. g. 10-100 Catalyst/oilweight ratio 10:1-30:1 Steam per cent of oll 0-25 The relative amountsof the light naphtha and flashed condensate available froma givenpetroleum depends upon the particular petroleum.

., the boiling range of the naphtha fraction, and

may be used. These materials may furthermore tion of gasoline would bequite low. The refrac which are invariably present. This material is thedepth of flashing, In some cases the available refractory naphtha, ofsay 3213-450 ,F. boiling range, may be more than enough to form asatisfactory blend with and may vary considerably.

increase the amount of flashed condensate. In

general ratios of flashed condensate to naphtha of from about 1:1 toabout 10:1 are preferred.

It is to be noted that according to the prevalent belief in the art, thedescribed mixture of flashed condensate and light naphtha would not beconsidered a desirable feed for catalytic cracking.-

The light naphtha, it will be noted, contains appreciable quantities,and may even consist essentially, of hydrocarbons which can properly beconsidered as gasoline components. In fact, the

light naphtha could in many cases also be called a heavy straight rungasoline. When crackin gas oil, stove oil,/and similar intermediatedistiilates, it is known that the presence of gasoline constituents inthe feed is quite harmful. The

prevalent belief in the art is that such gasoline components should beabsent from all catalytic cracking stocks. In the present process thisharmful effect of gasoline components isnot noticed, and, on thecontrary, the light naphtha in the present process is distinctlybeneficial in certain respects. Thus, the naphtha fraction is quiterefractory and is preferably cracked at high cracking temperatures. Whenthis material is cracked alone it is difllcult to maintain the optimumhigh cracking temperatures. Onthe other hand the flash condensates andflash cracked 1 large amounts of coke are formed and the conversions arelow, apparently due to the poisoning effect of these impurities. When,however, the

naphtha fraction and the flashed condensate or flash cracked condensateare cracked together these disadvantages tend to cancel each other,

to a certain extent. Thus, the naphtha tends to reduce the concentrationof nitrogen bases, etc. and the flashed condensate tends to increase thethermore, the flashed condensates and flash cracked condensates arequite heavy and difficult to maintain entirely in the vapor phasewithout the use of a large amount of'steam. The relatively light naphthaacts as a diluent and is very beneflcial in this respect also.

The above described modification of the present process, it will beseen, allows the production of considerable yields of excellent Dieselfuel from pressure and under mild cracking conditions to produce a heavyresidue and between 50% and 75% of a heavy flash cracked condensatehaving a molecular weight between about 280 and 300 with the formationof less than 1% gas and less than 1% gasoline, mixing said naphthafraction with a finely divided cracking catalyst and con-- veying themixture to the bottom of a cracking zone containing fluidized crackingcatalyst, introducing at an intermediate point in said cracking zonesaid heavy flash cracked condensate thereby to simultaneously crack saidnaphtha at a relatively low space velocity and said heavy flash crackedcondensate at a relatively high space velocity separating the crackedproduct into a gasoline fraction and a heavy aromatic condensate, andcombining said heavy aromatic condensate with said heavy residue toproduce fuel oil. a

2. In the production of useful products including gasoline and fuel oilfrom petroleum the process comprising separating the petroleum bydistillation into a naphtha fraction boiling between 300 F. and 500 F.,a heavy reflux condensate, and a reduced crude, subjecting the reducedcrude to a flash distillation under reduced pressure and under mildcracking conditions to produce a heavy residue andbetween 50% and 75% ofa flash cracked condensate having a molecular weight between about 280and 300 with the formation of less than 1% of gas and less than 1%gasoline, passing said naphtha through a catalytic cracking zone incontact with a fiuidized finely divided cracking catalyst, introducinginto the partly cracked naphtha in said cracking zone said heavy flashcracked condensate, thereby to simultaneously crack said heavy flashcracked condensate in the presence of partly crcaked naphtha, separatingthe cracked products into a gasoline fraction and a heavier aromaticcondensate and combining said heavier aromatic condensate with saidheavy flashed residue to produce fuel oil.

3. In the production of useful products includnig gasoline and fuel oilfrom petroleum, the process comprising separating the petroleum bydistillation into a naphtha fraction boiling be tween about 320 F. and450 F., a heavy reflux condensate, and a reduced crude, subjecting thereduced crude to a flash distillation under reduced pressure to producea heavy residue and between 40% and 75% of a heavy flashed condensatehaving a molecular weight between about 270 and 350,

mixing said naphtha fraction with a finely divided the virgin naphthawithout impairing the quantity or quality of gasoline produced. Thegasoline is produced largely from the flashed condensate or flashcracked condensate while taking advantage of some gasoline productionfrom the refractory naphtha and at the same time producing therefrom arefractory aromatic condensate which is compatible with flashed residueand flash cracked residue and may be used to convert these residues tosuperior fuel oils. Thus, the process allows the petroleum to beutilized to better advantage without sacrificing'yield or quality ofsecondary products.

cracking catalyst and conveying the mixture to the bottom of a crackingzone containing fluidized cracking catalyst, introducing at anintermediate point in said cracking zone said heavy flashed condensate,thereby to simultaneously crack said naphtha at a relatively low spacevelocity and said heavy flashed condensate at a relatively high spacevelocity, separating the cracked product into a gasolinefraction and aheavy aromatic condensate and combining said heavier aromatic condensatewith said heavy residue to." produce fuel oil.

4. In the production of useful products including gasoline and fuel oilfrom petroleum, the

tween 300 F. and 500 F., a heavy reflux condensate, and a reduced crude,subjecting the reduced crude to a flash distillation under reducedpressure to produce a heavy residue and between about 40% and 75% of aheavy flashed condensate'having a molecular weight between about 270 and350, passing said naphtha through a catalytic cracking zone in contactwith a fluidized finely divided cracking catalyst, introducing into thepartly cracked naphtha in said cracking zone said heavy flashedcondensate, thereby to simultaneously catalytically crack said heavyflashed condensate in the presence of partly cracked naphtha, separatingthe cracked products into a gasoline fractionand a heavier aromaticcondensate and combining said heavier aromatic condensate with saidheavy flashed residue to duce fuel oil.

5. In the production of useful products including gasoline and fuel oilfrom petroleum, the process comprising separating the pe r m ydistillation into a naphtha fraction boiling between about 320 F. and450 F., a heavy reflux condensate, and a reduced crude, subjecting thereduced'crude to a flash distillation under reduced. pressure to producea heavy flashed con-v densate and a heavy residue, mixing said naphthafraction with a finely divided cracking catalyst and conveying themixture to the bottom of a cracking zone containing fluidized crackingcataprolyst, introducing at an intermediate point in said.

cracking zone said heavy flashed condensate, thereby to simultaneouslycrack said naphtha at process comprising separating the petroleum by'distillation into a naphtha fraction boiling bea relatively low spacevelocity and said heavy flashed condensate at a relatively high spacevelocity, separating the cracked product into a gasoline fraction and aheavy aromatic condensate and combining said heavier aromatic condensatewith said heavier residue to produce fuel oil.

.6. In the productionof useful products including gasoline and fuel oilfrom petroleum, the process comprising separating the petroleum bydistillation into a naphtha fractionboilingibetween 300 F. and 500 F., aheavy reflux condensate, and a reduced crude, subjecting the reducedcrude to a flash distillation under reduced pressure to produce a heavyflashed condensate and a heavy flashed residue, passing said naphthathrough a catalytic cracking zone in contact with a fluidized finelydivided cracking catalyst, in-

troducing into the partly cracked naphtha in said cracking zone saidheavy flashed condensate,

thereby to simultaneously catalytically crack said heavy flashedcondensate in the presence of partly cracked naphtha, separating'thecracked products into a gasoline fraction and a heavier aromaticcondensate, and combining said heavier aromatic condensate with saidheavy flashed residue to produce fuel oil.

' JOHN M. BRACKENBURY.

, I REFERENCES crrEn The following references are of record in the fileof this patent:

UNITED STATES PATENTS Bailey Sept. 25. 1945

